Microservices: A retrospective

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Microservices: A Retrospective Tomer Gabel @ Reversim Summit, 2019

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Agenda 1. Why oh why 2. Lessons learned 3. Lessons not learned 4. The big reveal Image: Today's Menu by Hypnotica Studios Infinite via Flickr (CC BY 2.0)

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Technology malcontent Who am I? Engineer @ Organizer Reversim Summit alumnus x7

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1. WHY OH WHY Image: 40+216 Faces by bark via Flickr (CC BY 2.0)

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Why do Microservices? • Developer velocity – Independent releases – Limited scope of work – Stronger decoupling • All thanks to bounded context Image: Playing on the Merry go round by Charles Knowles via Flickr (CC BY 2.0)

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Why do Microservices? • Scalability – Independent scaling – Independent storage – Limited scope is easier to optimize • All thanks to bounded context Image: Skyscraper Under Clear Day Sky via Pixabay (Pixels license)

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• Resilience – Strict error boundaries – Partial failures • Secondary benefits – Polyglot – Easier to test (maybe?) • Yup: also thanks to bounded context Why do Microservices? Image: Building collapse in Łódź, Sienkiewicza & Tuwima Streets, November 2015 by Zorro2212 (CC BY-SA 4.0)

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ORGANIZATIONAL SCALING Nah. It’s all about

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Let me explain • A successful organization grows – More products – More teams – More visibility – More liability – More responsibility! Image: Evolution Logo Wikimedia by Johanna Pung (CC BY-SA 3.0)

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Let me explain • But as you grow… • Products become interdependent – And so do teams – Incurring a synchronization cost • “… so what”, you say? Image: SVG Graph illustrating Amdahl's law by Daniels220 (CC BY-SA 3.0)

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Let me explain • Four metrics of high- performing† organizations: – Lead Time – Deployment Frequency – MTTR – Change Fail Percentage • All negatively affected by synchronization! † Per “Accelerate” by Forsgren, Humble and Kim (IT Revolution Press, 2018)

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Let me explain • So we’re shooting for: – Minimizing synchronization – Maximizing independence • Microservices are a great fit! Image: Aerial view of Watsonville, California, USA by Robert Campbell (CC BY-SA 3.0)

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2. LESSONS LEARNED

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Small is Good • Less code = less bugs • Smaller interfaces – Easier to reason about – Easier to evolve – (hard to keep small) • Results in lower coupling

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Polyglot Ahoy Company # Languages Google 6 Facebook 9 Twitter 4 Amazon 3 Netflix ~3 Spotify 4 • The great promise of microservices • Multiple stacks! • You ain’t gonna need it • You ain’t gonna want it • But it sure feels nice

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Conway Knows “Organizations which design systems [...] are constrained to produce designs which are copies of the communication structures of these organizations.” -- Melvin E. Conway

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Conway Knows • Common danger signs: – One data store owned by multiple services – Single system owned by multiple teams • If you’re violating SRP… – Reorganize your services – … or your teams! Image: 03053904 by Jerry Norbury via Flickr (CC BY-ND 2.0)

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Operations Matter • Developer velocity = ship fast and strong • No bottlenecks allowed! – Global release – Centralized ops – Manual deployment – Static topology

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Operations Matter • Developer velocity = ship fast and strong • No bottlenecks allowed! – Global release ⇨ Many small, rapid iterations – Centralized ops – Manual deployment – Static topology

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Operations Matter • Developer velocity = ship fast and strong • No bottlenecks allowed! – Global release ⇨ Many small, rapid iterations – Centralized ops ⇨ Distributed ownership – Manual deployment – Static topology

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Operations Matter • Automation is key – Infrastructure – Deployment – Monitoring – Remediation – Provisioning • Automation empowers your teams!

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3. LESSONS WE HAVEN’T LEARNED Image: “If at first you don't succeed...” by Adam Fagen via Flickr (CC NC-SA 2.0)

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The Laws of Physics We wouldn’t design an airplane … while ignoring this guy Images: Landing at Madrid-Barajas airport by José A. Montes (CC BY 2.0) and Portrait of Sir Isaac Newton, oil on canvas (public domain)

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The Laws of Physics Why, then, do we ignore them … when designing these? Images: Leslie Lamport (from personal site), Eric Brewer at TNW Conference (CC BY-SA 4.0), and A diagram of the proposed system architecture by EpochFail (CC BY-SA 3.0)

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The Laws of Physics • We are all building distributed systems • Concurrency is key • Disregarding CAP means… – You will end up with inconsistent data – You will not scale – You will lose data Image: The Scream by Edvard Munch (public domain)

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Observability • Distributed systems are, by nature… – Disaggregate – Hard to reason about • We are still deficient – In tooling – In methodology Image via PXHere (CC0 public domain)

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Observability • Tooling is getting better! – Tracing (Jaeger, Zipkin) – Metrics (Grafana, Prometheus) – Log aggregation (ELK et al) • … but that’s not enough

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Observability • When you can’t debug in isolation… • You have to know: – What to log – What to count – What to monitor – How to make sense of it all!

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4. THE BIG REVEAL Image: The Unveiling by nate.stevens via Flickr (CC BY-NC-ND 2.0)

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Quick Recap • We aim to: – Minimize synchronization – Maximize independence • We’re struggling with: – Safety – Scalability – Observability Image: Retrospective - Good by Denis De Mesmaeker via Flickr (CC BY-NC-ND 2.0)

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Events • They are your friends • Events make everything simpler • No, really. Much simpler • Let’s explore how Image: Ledger by Shea Smith via Flickr (CC BY 2.0)

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Events • Modeling interactions with events: – Enforces strong context boundaries – Lets you scale services independently – Lets you observe the system in motion – Increases system reliability Client User Service Onboarding Service Search Service Analytics Event Bus RPC

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Events • Persisting event streams (event sourcing): – Observability is built in! – (as is auditing) – Lets you scale use cases independently (CQRS) • Precludes full consistency – This is a good thingTM Opened Account Deposited $100 Withdrawn $25 Deposited $12 Balance: $87

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Events • Modeling workflows in terms of events… – Enables sagas – A pattern for cross- domain consistency – A viable alternative to transactions! – (in most cases) Sagas, Garcia-Molina and Salem, SIGMOD 1987

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SWEAT THE PRINCIPLES Not the implementation details.

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Commoditization • A lot has changed • We have tools now! – gRPC, Thrift, Avro – Kafka – Docker, Kubernetes – Spinnaker • No need to roll your own (less so, anyway)! Image via opensource.com (CC BY-SA)

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Expertise • Invest in studying: – CAP tradeoffs – Domain modelling – Event storming – Event sourcing/CQRS – Sagas • You’ll be better off! Image: Back to School by Phil Roeder via Flickr (CC BY 2.0)

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Further Reading Design Microservice Architectures the Right Way Michael Bryzek An Abriged Guide to Event Sourcing Tomer Gabel

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QUESTIONS? Thank you for listening tomer@tomergabel.com @tomerg On GitHub: https://github.com/holograph This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.